WASHINGTON (AP) — The Trump administration on Friday missed another deadline to produce President Donald Trump's tax returns. A top House Democrat said he expects to take the administration to court as early as next week over the matter.

Treasury Secretary Steven Mnuchin said in a letter that he will not comply with a subpoena from House Ways and Means Committee Chairman Richard Neal for six years of Trump's tax returns because the request "lacks a legitimate legislative purpose."

Mnuchin's rejection of the subpoena had been expected. Earlier Friday, Neal had said, "We will likely proceed to court as quickly as next week."

Asked if he might seek to hold Mnuchin in contempt of Congress for his refusal to supply the tax returns, Neal said, "I don't see that right now as an option. I think that the better option for us is to proceed with a court case."

Democrats are seeking Trump's tax returns under a 1924 law that directs the IRS to furnish such information when requested to the chairs of Congress' tax-writing committees.

In a statement Friday after Mnuchin's decision was announced, Neal said that the law "does not allow for discretion as to whether to comply with a request for tax returns and return information."

In his statement, Neal said he would consult with committee lawyers "on how best to enforce the subpoenas moving forward."

Besides Trump, every president since Richard Nixon has made his tax returns public.

In a tweet on May 10, Trump said that he had won the presidency in 2016 "partially based on no Tax Returns while I am under audit (which I still am), and the voters didn't care. Now the Radical Left Democrats want to again relitigate the matter. Make it part of the 2020 Election!"

When he issued the subpoena last week, Neal said he was seeking six years of Trump's personal and business tax returns to aid a committee investigation into whether the IRS is doing its job properly to audit a sitting president and whether the law governing such audits needs to be strengthened.

In his letter Friday saying he would not comply with the subpoena, Mnuchin said he had consulted with the Justice Department and had been advised that he was not authorized to turn over the tax returns because Neal's request did not represent a legitimate congressional purpose.

Mnuchin said that while he will not turn over Trump's tax returns, he has offered to work with the congressional panel "to accommodate its stated interest in understanding how the IRS audits and enforces the federal tax laws against a president" by providing the committee with information on the mandatory audit process for presidential returns.

The fight with Congress over Trump's tax returns is one of a number of battles House Democrats are having with the administration over the release of information. The House Judiciary Committee has voted to hold Attorney General William Barr in contempt and is fighting to obtain an unredacted report prepared by special counsel Robert Mueller on Russian interference in the 2016 election.

This trip, the first of two President Donald Trump is expected to make to Japan in the next six weeks, is more of a social call meant to highlight the alliance between Japan and the United States and the friendship between their leaders.